GLASS FIBER FORMING COMPOSITION, GLASS FIBERS OBTAINED FROM THE COMPOSITION AND SUBSTRATE FOR CIRCUIT BOARD INCLUDING THE GLASS FIBERS AS REINFORCING MATERIAL

摘要

A glass fiber forming composition exhibits a remarkablyhigh dielectric constant .epsilon.r as well as superior chemicalresistance, yet it is readily spun into glass fibers. Thecomposition is characterized to show a devitrificationtemperature which is lower than a spinning temperature atwhich the glass composition exhibits a viscosity of 102.5poise, so as to be readily spun into corresponding glassfibers. The composition consists essentially of 40 to 65mol% of SiO2; 20 to 45 mol% of at least one componentselected from the group consisting of MgO, CaO, SrO and BaO;5 to 25 mol% of at least one component selected from thegroup consisting of TiO2 and ZrO2; and 0.5 to 15 mol% ofNbO5/2 as calculated from an incorporated amount of Nb2O5.Alternately, the composition consist essentially of 40 to 65mol% of SiO2; 20 to 45 mol% of at least one componentselected from the group consisting of CaO, SrO and BaO; 5 to25 mol% of at least one component selected from the groupconsisting of TiO2 and ZrO2; 0.5 to 15 mol% of NbO5/2 ascalculated from an incorporated amount of Nb2O5; and 0.5 to15 mol% of AlO3/2 as calculated from an incorporated amountof Al2O3. The composition is also characterized toincorporate at least 85 mol% of a total amount of the oxidesand have a dielectric constant [.epsilon.r] of 9 or more at 1 MHzand 25°C.